For size, I think that 5/8 to 6/8 is a good place to start. The razors are easy to manuver than larger razors (I can shave under my nose with an 8/8, but I've had some practice at it), but there is still enough blade there to let you really watch your angle. With smaller blades, it's very easy to all of a sudden find yourself shaving at a very high angle without realizing it.

Another plus for 5/8 - 6/8's is that they are readily available at all prices, so they are very easy to shop for.

As for the grind, I don't think there is a clear choice. The way I see it is this:
A full hollow is like tough love - You need better technique to get a great shave from a full hollow, so it will force you to improve quickly
A half hollow (or heavier) will coddle you - They are more forginving of poor technique, so you'll start off more easily, but it won't hilight your mistakes and force you to fix them.